Polyimide for silicon solar cells with double-sided textured pyramids

• Published in: Solar energy materials and solar cells Vol. 183; pp. 200 - 204
• Main Authors: Zin, Ngwe, McIntosh, Keith, Bakhshi, Sara, Vázquez-Guardado, Abraham, Kho, Teng, Fong, Kean, Stocks, Matthew, Franklin, Evan, Blakers, Andrew
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2018; Elsevier BV
• Subjects: ALD AlOx; Back-contact; Cytology; Diffusion; Diffusions; Electric contacts; Electrical insulation; High efficiency; IBC; Interlayers; Passivation; PECVD nitride; Photoelectric effect; Photoelectric emission; Photovoltaic cells; Pinholes; Polyimide; Pyramids; Ray trace; Rear texture; Recombination; Reflectance; Silicon; Silicon nitride; Simulation; Solar cell; Solar cells; Surface layers; Texture; Trapping; Solar cell; Polyimide; PECVD nitride; High efficiency; Diffusions; ALD AlOx; Back-contact; IBC; Rear texture; Ray trace; Passivation
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2018.03.015

Silicon solar cells incorporating double-sided pyramidal texture are capable of superior light trapping over cells with front-side only texture. However, increased surface area, roughness and exposed crystal planes of textured surfaces not only causes increased recombination, but also makes cells susceptible to shunting through pinholes in the dielectric at the sharp peaks and valleys of the textured pyramids. A polyimide film as an insulating interlayer film is investigated to circumvent the tradeoff between improved light trapping, increased recombination and increased shunt paths. When applied at the rear of the interdigitated back contact silicon solar cell structure, the polyimide film provides an excellent electrical insulation (> 1000 MΩ of insulation resistance) and increases photocurrent (~ 1.1 mA/cm2) owing to an increased rear internal reflectance. The polyimide is also compatible with metal annealing of passivating dielectrics such as silicon nitride. Optical simulation and experimental results are combined in a 3D semiconductor simulation (Quokka) to quantify the possible gain of implementing the double-sided texture in high efficiency silicon solar cells.
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The polyimide film between the rear metal and passivated pyramidal textured surface of the silicon structure demonstrates:
•The polyimide (PI) film demonstrates an excellent insulation resistance (> 1000 MΩ).•PI increases the absorption within the silicon (ΔJGen = 1.1 mA/cm2 compared to the structure with a planar rear and no polyimide film).•PI is compatible with metal annealing of passivating dielectrics.•Incorporating PI between the metal and passivated pyramidal texture at the rear would increase the conversion efficiency of IBC silicon solar cells by 0.3%.